流媒体服务中即时响应的层次存储数据放置策略.pdfVIP

计算机科学2004VoI.贝岭.9 流媒体服务中即时晌应的层次存储数据放置策略铃〉 徐尧强邢春晚周立柱 (清华大学计算机科学与技术系 北京100084) 摘要 为了~得松岛的性能价格比.i，U革体服~ß通常采用层次存储技术.由于三级存储设备的机械特性.访问层 次存储革tt(HSM) 中的数据常委很长的响应时间.本文提生了具有即时响应性能的敷据放:1.方法:.re.i，1Ì.媒体对阜特 定长度的头部生据预允放亘在磁盘土，而敛4屠讲~首先从 HSM 的敏盆土得到响应.4.该取秘盒数据期间进行三级存 铺设备的准晶.在特定的头部疆生据长1史以及琪比弄法下.可以消除访问三级存储说品需要的等待时间.本文始出了此 头tJt疆生精长度的计算方法，(及 HSM 的敛槐该取其法.仿真试验农明，只笃较小的存储代价，革t可以使得 HSM ß:锐的 响应时间太太降低.而且数揭具有良好的连贯性，从而提高了整个黑锐的性L 关键询 层次存储，继休戚井嚣，敛据放豆 An I mmed iat ely Resp on Sible D at a Placem ent Method of Hierarchical Storage Man ag em ent for Streaming Media Server XU Yao-Qiang XING Chun-Xiao ZHOU Li-Zhu (Depament 01 Computer Sc;ience and Technology. T.inghua Univeni町.8刷jing 100084) Abst ract Hierarchical storage t时hnology is used in mcdia servers to get high performance/cost r8tio. However. in traditional hierarchical storage system (HSM).the data.say a movie.is usually placed wholly in a tertiary storage de- 叽四. Thus. the response time to U$町、 request will be too long to be satislactory. This paper prescnt5 a new data placement method based on prearrangement strategy in HSM lor streaming media ser ver. By prearranging the head part 01 media objecls wilh specified length on d出k. slreaming data 8ccesses can gel immedialc rcsponse. and in the meantime. tertiary storage device can be ready for continuous acce.s. The pap盯 give. a method to calculate the head data lenglh o( media objects and an algorithm to read data in HSM. Simu.lation resuh shows t hat with a low disk 5t时­ age c。剖. the response time 01 the HSM system can be 陀duced to a large exte时• and the performance of the whole sys- tem is enhanced significantly. Keywords Hierarchical 剖